parent proxy failover on 404

[Mateusz Zajakala <za...@gmail.com>]

Hi,

I have parent proxy config where my frontend hosts ATS (5.3.0), which
remaps all requests to origin1, however uses parent config with origin2
acting as parent:

map / http://origin1/

dest_host=origin1 parent="origin2:80" go_direct=true

This works fine and provides nice failover if origin2 goes down (ATS begins
forwarding requests to origin1 as expected), however I'm not sure how to
handle a case when origin2 is online, but due to service breaking down the
files to be served are no longer there (HTTP 404).

ATS logs TCP_MISS/404 but considers all 404 responses from origin2 as
PARENT_HIT (text/html).

How do I instruct ATS that 404 is in fact not a 'HIT' and should cause ATS
to go to origin1? Is it possible?

Thanks!
Mat

Re: parent proxy failover on 404

[James Peach <jp...@apache.org>]

> On Aug 30, 2016, at 8:11 AM, Mateusz Zajakala <za...@gmail.com> wrote:
> 
> Hi,
> 
> I have parent proxy config where my frontend hosts ATS (5.3.0), which remaps all requests to origin1, however uses parent config with origin2 acting as parent:
> 
> map / http://origin1/
> 
> dest_host=origin1 parent="origin2:80" go_direct=true
> 
> This works fine and provides nice failover if origin2 goes down (ATS begins forwarding requests to origin1 as expected), however I'm not sure how to handle a case when origin2 is online, but due to service breaking down the files to be served are no longer there (HTTP 404).

https://docs.trafficserver.apache.org/en/latest/admin-guide/files/parent.config.en.html

You could set unavailable_server_retry_responses=404, but that would consider the parent unavailable for all requests. Probably a bit aggressive :-/

> 
> ATS logs TCP_MISS/404 but considers all 404 responses from origin2 as PARENT_HIT (text/html).
> 
> How do I instruct ATS that 404 is in fact not a 'HIT' and should cause ATS to go to origin1? Is it possible?
> 
> Thanks!
> Mat